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A font-display setting for slow connections

Me, I really dislike FOUT. I like that it’s an option, because not displaying text quickly on the web is no good. I know font-display: swap; is popular because it’s good for performance, but that FOUT stuff pains me. Matt Hobbs:

If there’s one thing I’d like readers to take away from this post it’s that font-display: swap is a very good option for users with a fast internet connection. But its infinite swap period could be frustrating for users on very slow and unstable connections. If you have users viewing your site under these conditions (I’m pretty certain you will at some point in time), then it may be worth considering font-display: fallback or even font-display: optional.

Seeeee, I told ya. I like how font-display: optional; totally stops FOUT. The font is either applied super fast, or isn’t used at all (but still downloaded async). Chances are, on the next page load, the font is loaded and cached and will be used.

Note this is about slow connections, not necessarily connections where the user would prefer as little data usage as possible. If that’s the case, check out some of the recent posts we linked up in Responsible, Conditional Loading.

And boy howdy, the Web Performance Calendar this year was just loaded in great articles.

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Web Performance Calendar

The Web Performance Calendar just started up again this year. The first two posts so far are about, well, performance! First up, Rick Viscomi writes about the mythical “fast” web page:

How you approach measuring a web page’s performance can tell you whether it’s built for speed or whether it feels fast. We call them lab and field tools. Lab tools are the microscopes that inspect a page for all possible points of friction. Field tools are the binoculars that give you an overview of how users are experiencing the page.

This to me suggests that field tools are the future of performance monitoring. But Rick’s post goes into a lot more depth beyond that.

Secondly, Matt Hobbs wrote about the font-display CSS property and how it affects the performance of our sites:

If you’re purely talking about perceived performance and connection speed isn’t an issue then I’d say font-display: swap is best. When used, this setting renders the fallback font almost instantly. Allowing a user to start reading page content while the webfont continues to load in the background. Once loaded the font is swapped in accordingly. On a fast, stable connection this usually happens very quickly.

My recommendation here would be to care deeply about the layout shift if you use this property. Once the font loads and is swapped out you could create a big shift of text moving all about over the place. I once shipped a change to a site with this property without minding the layout shift and users complained a lot.

It was a good lesson learned: folks sure care about performance even if they don’t say that out loud. They care deeply about “cumulative layout shift” too.

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Google Fonts is Adding font-display

Google announced at I/O that their font service will now support the font-display property which resolves a number of web performance issues. If you're hearing cries of joy, that's probably Chris as he punches the air in celebration. He's wanted this feature for some time and suggests that all @font-face blocks ought to consider using the property.

Zach Leatherman has the lowdown:

This is big news—it means developers now have more control over Google Fonts web font loading behavior. We can enforce instant rendering of fallback text (when using font-display: swap) rather than relying on the browser default behavior of invisible text for up to 3 seconds while the web font request is in-flight.

It’s also a bit of trailblazing, too. To my knowledge, this is the first web font host that’s shipping support for this very important font-display feature.

Yes, a big deal indeed! You may recall that font-display instructs the browser how (and kinda when) to load fonts. That makes it a possible weapon to fight fight FOUT and FOIT issues. Chris has mentioned how he likes the optional value for that exact reason.

@font-face {
  font-family: "Open Sans Regular";
  src: url("...");
  font-display: optional;
}

Oh and this is a good time to remind everyone of Monica Dinculescu’s font-display demo where she explores all the various font-display values and how they work in practice. It’s super nifty and worth checking out.

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